Appendix:Mega Evolution

Mega Evolution is a transformation that only appears in certain final form Pokémon, or some Pokémon that cannot evolve. Mega-Evolved Pokémon are identified by having "Mega" in front of their name. Mega Evolution can only be achieved if there is a strong bond between a Trainer and its Pokémon.

Summary
In order to Mega Evolve, most Pokémon must be holding their appropriate Mega Stone and the Trainer must have a Key Stone. Only Rayquaza does not require a Mega Stone to Mega Evolve -- instead, it must know the move Dragon Ascent. In any battle, each Trainer may Mega Evolve a single Pokémon once. Mega Evolution is essentially a free action a Pokémon may make in addition to its normal move, but if a Pokémon will not use a move, it cannot Mega Evolve. Mega Evolution occurs before most actions except switching. A Mega-Evolved Pokémon will only revert back to its original state if it faints or the battle ends; if it is withdrawn, it will still be in its Mega Evolved state once switching back in.

A Pokémon cannot Mega Evolve if it is being held in the airborne phase of Sky Drop. Neither volatile nor non-volatile status conditions such as paralysis, sleep, and infatuation will have any effect over a Pokémon's ability to Mega Evolve; even if they result in the Pokémon not being able to move that turn, the Mega Evolution will occur regardless.

Mega Stones are not affected by most moves or Abilities. If they would move a Mega Stone to or from a Pokémon that could use it to Mega Evolve, the moves Bestow, Covet, Fling, Thief, Trick, and Switcheroo will fail and the Abilities Magician, Pickpocket and Symbiosis will not activate. The move Knock Off cannot remove a Mega Stone from a Pokémon that can use it to Mega Evolve, and Knock Off's power will not be increased since it cannot remove the item. The moves Embargo and Magic Room, as well as the Ability Klutz, will not prevent a Pokémon from using its respective Mega Stone to Mega Evolve.

Performing Mega Evolution will not alter the attacking order during the Mega Evolving turn, so a Pokémon with a lower Speed than their opponent will still go after them on the one turn the Mega Evolution occurs, even if their Mega Evolution increases Speed and would otherwise cause them to go first. The opposite is also true for Pokémon who lose Speed from Mega Evolution, such as Garchomp. Attacking order will be determined normally on every turn afterwards. The newest core series games Pokémon Sun and Moon has fixed this problem, such that the attacking order during the Mega Evolving round will now also be decided by the Speed stats after Mega Evolution, yet it is unknown if this correction will be carried to Pokémon Brick Bronze in later updates.

All other stat changes and type changes of a Mega Evolution will take effect immediately and damage calculation will proceed as usual -- a Pokémon whose Mega Evolution possesses a lower Defense stat will take greater damage from Physical attacks on the turn of Mega Evolving. Changes in a Pokémon's Ability will also take place immediately. For example, a Sharpedo that normally has Speed Boost will not gain a boost in Speed at the end of the turn it Mega Evolves, but if it uses a biting move such as Crunch that turn, it will be boosted by Strong Jaw, its Ability as Mega Sharpedo.

Key Stone
To obtain the Key Stone, player must encounter the Eclipse Boss for a battle in Anthian Park, Anthian City. Before the battle begins, Rival Tess will give her Key Stone to the player in order to Mega Evolve the Absol that rushes in to help. Unlike in core series games, the Key Stone is not carved in a Mega Ring, Mega Bracelet or any unique accessories.

Mega Stone
Like in core series game Pokémon X and Y, where Mega Evolution is first introduced, Mega Stones can be found by various methods listed below.

Event
The Abomasite was given along with a Shiny Snover during the 2015 Christmas Event held on Route 8, which ended on 31st December, 2015.

Given in Plot
The Absolite is held by the Absol which automatically joins the player right before the boss battle in Anthian Park.

Purchase
28 kinds of Mega Stones can be bought, with 19 sold at the Stone Shop in Anthian City - Shopping District, and another 9 available at the BP Shop in Battle Colosseum.

List of Mega Evolutions
Note: Italics indicate Hidden Abilities of a Pokémon.

Primal Reversion
Primal Reversion is an ancient transformation of Pokémon. Pokémon that have undergone Primal Reversion are distinguished by the word "Primal" in front of their species name. It is similar to Mega Evolution, but instead of using the energy of people and Pokémon, the user instead absorbs the energy of nature to greatly increase its power. Primal Reversion is said to restore the true powers of a Pokémon.

In order to undergo Primal Reversion, a Pokémon only needs to be holding the appropriate Orb. Like Mega Stones, Orbs cannot be knocked off, thrown or stolen by any moves or abilities if held by the appropriate Pokémon. Unlike Mega Evolution, however, the player does not need a Key Stone or have to manually trigger Primal Reversion; it will simply happen automatically after the Pokémon enters battle and after any entry hazards take effect, but before the activation of weather-changing Abilities. Also unlike Mega Evolution, there is no limit to the number of times a Primal Reversion may be performed per battle.

Only 2 Pokémon are able to perform Primal Reversion: Kyogre and Groudon, members of the "Weather Trio". The final member of "Weather Trio" -- Rayquaza, despite having its signature Orb as well, undergoes Mega Evolution instead, along with some other Legendary Pokémon.